Due to the avoidance of first-pass hepatic metabolism and gastrointestinal irritation, intravaginal administration is an attractive option for systemic delivery of drugs. Current vaginal drug delivery studies are primarily performed using the FDA-accepted rabbit model. However, such studies are costly and time consuming. In addition, animal experiments are often highly variable. To avoid these problems, we propose use of a highly differentiated and reproducible, in vitro reconstructed human vaginal ectocervical (VEC) tissue model such as MatTek EpiVaginalTM model. However, the barrier properties of the EpiVaginal model need to be optimized so that they accurately match those of native in vivo tissue. . Phase Iresearch will produce various EpiVaginal cultures in which the tissue phenotype has been modified. These tissues will be characterized in terms of histology, barrier properties (measured by transepithelial electrical resistance), and the presence of organelles important in determining mucosal barrier properties such as desmosomes and tight junctions. In addition, the levels of barrier lipids will be quantified. The most promising tissues will be selected for drug permeability studies using a set of model drugs for which historical pharmacokinetic intravaginal rabbit data are available. The in vitro and in vivo data will be compared to choose the tissue with optimized barrier properties. Finally, the economics of utilizing the in vitro tissue model for pre-clinical intravaginal drug delivery studies versus rabbit studies will be compared. PUBLIC HEALTH RELEVANCE: The vaginal route has a great potential for systemic drug delivery due to its large surface area, high vascularization, permeability to a wide range of compounds including peptides and proteins, and avoidance of the hepatic first-pass metabolism and gastrointestinal irritation. Since drug absorption potential has become important criterion for decisions early in the drug discovery process, there is a great need to develop a reliable screening method for drug adsorption through the vaginal route. This proposal will optimize a highly differentiated, human vaginal tissue model to facilitate such studies.